Meeting Abstract

17.1  Jan. 4  The energetics of quadrupedal and bipedal locomotion in chimpanzees RAICHLEN, D.A.*; PONTZER, H.; SOCKOL, M.D.; University of Arizona; Washington University; University of California, Davis raichlen@email.arizona.edu

For decades, researchers have worked to discover general principles governing the energetic costs of terrestrial locomotion. The Force Production Hypothesis satisfies many of the requirements of a general explanation. The muscle force produced to support body weight explains differences in the energetic costs of locomotion between organisms that differ in body size, between organisms of similar size yet with very different limb designs, and within an organism but between walking and running. In this study, we show that force production also explains the difference in cost within individuals using vastly different locomotor postures. Chimpanzees are able to walk and run both quadrupedally and bipedally, with bipedalism generally more energetically costly than quadrupedalism. We measured energy expenditures, kinematics and kinetics for a sample of three chimpanzees using both bipedal and quadrupedal locomotion. We estimated active muscle volumes for each gait using inverse dynamics and compared muscle volumes with energy expenditures. Differences in energy expenditure between bipedal and quadrupedal locomotion are well explained by differences in muscle force production and the amount of muscle volume activated, adding further support to this general explanation of locomotor costs in terrestrial organisms.